The present invention relates generally to electronic test instruments and more particularly to a test probe assembly for electrically connecting a ball grid array surface mount package to an electronic measurement device.
Ball grid array (BGA) has become the package of choice in the surface mount technology arena. BGA""s offer many advantages over standard fine-pitch surface mount and pin grid array technologies. These advantages include reduced placement problems since BGAs are self-centering, reduced handling issues because there are no leads to damage, lower profile and higher interconnect density. There is, however, a significant drawback with BGA technology: the lack of established BGA test accessories and procedures.
Electronic test instruments (e.g., oscilloscope, logic analyzer, emulator) are used to analyze various electrical aspects of the IC including voltage and current waveforms. Typically, a loaded printed circuit board is crowded with various electrical components, including multiple IC packages. Due to the close spacing of components on the board (i.e., high xe2x80x9cboard densityxe2x80x9d) it is often difficult to electrically connect the ICs to the test instrument. BGAs tend to exacerbate this problem since there are no xe2x80x9cleads to access for testing purposes.
As processor packages become more dense due to electric al requirements, it has become increasingly difficult to probe these packages. With pin counts in the 600-700 range, and pin to pin spacing now at 0.050 inches or less, it has become necessary for motherboard sockets to go to BGA style packages vs. the former pin grid array (xe2x80x9cPGAxe2x80x9d) packages. This trend has increased the difficulty in reliably dividing and attenuating signals within the interstitial array of pins.
Also, increasing pin counts and pin densities increases the insertion force required to insert the processor into a conventional low insertion force socket. Typically, the collective insertion force required to insert a 603 pin processor is approximately 55-60 lbs. of force.
The present invention provides a BGA-PGA-Flex probing system. Advantageously, the invention allows use of a user""s pre-existing BGA socket while continuing to use a method of egressing signals from a PGA using flexible circuit material. The invention also allows replacement of a Low-Insertion Force (xe2x80x9cLIFxe2x80x9d) socket with an adaptation of a user""s BGA Zero-insertion Force (xe2x80x9cZIFxe2x80x9d) socket.
Accordingly, a user can easily insert a processor package into a probe according to the invention without damage to the silicon. The BGA-PGA-Flex probing system of the invention offers an electrically and mechanically superior interface to existing interposing probes for high-density processor packages. Advantageously, the current invention allows a user to utilize existing ZIF sockets. Implementation of a user""s socket into the probing system of the invention makes processor bus simulations easier due to fact that a user will already have simulated the socket by itself. The invention also offers the advantage of a ZIF socket versus a LIF socket.
In a preferred embodiment, the present invention comprises an unsealed BGA socket, nail head pins which can be inserted flush into a pin carrier to produce a PGA header, a Flex circuit assembly comprising a piece of flexible circuit with various passive resistors and connectors attached and solder preforms used to solder the flex assembly to the pin grid array.